Duplex telegraph



(No Model.) -2Sheets-Sheet 1. B THOMPSON.

DUPLEX TELEGRAPH.

' No. 261,78&.

Patented July 25, 1 882.

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i lfim L q ATTEST! 2 Sheets-Sheet 2.

(No Model.) 7 B THOMPSON.

DUPLEX TELEGRAPH. m- No. 261,788. Pa tented July 25, 1882;

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- l F M I I IM g a E IINVENTCIR! vATTE-T: I I i @WW l UNITED STATESPATENT OFFICE.

BENJAMIN THOMPSON, OF BUFFALO, NEW YORK.

DUPLEX TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 261,788, dated July 25,1882,

' Application filed May 27,1es2. (No model.)

To all whom it may concern:

Be it known that I, BENJAMIN THOMPSON, a citizen of the United States,and a resident of Buffalo, in the county of Erie and State of New York,have invented a certain new and useful Improvement in Duplex Telegraphs,of

' which the following is a specification.

The object of my invention is to form a simple and effective duplextelegraph without the use of condensers, equating-rheostats ordifierential relays.

My invention consists in the combination, with any ordinary relay andtransmitter, both located at the same station, of a differentiallywoundsounder or receiving-instrument, the circuit of one of whose coils iscontrolled by the movements of the transmitter in such a way that bothcoils are simultaneously broken or closed when the transmitter isoperated one coil by the movement of the transmitter and the other inthe-ordinary manner by the movements of the relay-armature. As anillustration of the principle, letit be supposed that normally bothdifferential coils are broken, and that the sounder-1ever be against itsback stop. If the transmitter be operated to send a signal to thedistant station, the arrangement is such that both coils will besimultaneously closed, one by the movement of the transmitter and theother by the relay-armature lever; but no signal will be given upon thesounder, because one-coil will neutralize the action of the other. Ifunder this condition a signal come from the distant station, therelay-armature willfall back, the two line-batteries neutralizing oneanother, thus breaking one differential coil, whereupon the other willact and draw down the sounder-lever. This general principle admits ofvarious modifications with regard to the normal condition of the localcircuits-that is, whether open or closed-and also with respect to thenormal polarity of the mainline batteries. Some of these modificationswill be hereinafter described. The invention, however, is not limited tothose described, as it consists broadly in rendering the sounder of thehome stationinsensible to outgoing signals by the aid of an extra ordifferentially-wound coil, the circuit of which is controlled by themovements of the transmitter-lever, the other differentially-wound coilbeing controlled in the ordinary way by the action of the home relay.

In the accompanying drawings, Figure 1 is a diagram of an apparatusconstructed and arranged according to my invention, and illustrates theapplication of the invention to an ordinary duplex telegraph. Fig. 2 isa diagram showing a modification of the devices operating with thetransmitter to open and close one coil of the differential sounder orreceiving-instrument. Fig. 3 illustrates the manner of applying theinvention to a duplex telegraph in which batteries of opposite polarityare used at the two ends of the line.

Referring to Fig. l, A and B represent the two distant stations of aduplex-telegraph line fitted with a similar apparatus. It will besufficient to describe the apparatus with reference to one station-as,for instance, A-that at the other station being similar and similarlymarked.

R represents a relay of any ordinary construction. T is a transmitteroperated in the ordinary way by a local electro-magnet and key, asindicated, and provided with the ordinary continuity-preserving contactsat D, by means of which the main battery M B is connected to anddisconnected from line. A rheostat, connected in theusual way, in thegroundwire, which is connected to transmitter-lever, and adjusted toequal resistance of the main battery, is shown at r.

S represents a sounder, wound differentially in a welLknown way, withtwo sets of coils, so that when a current flows simultaneously in themthey will neutralizeeach others effects, and the armature-lever will notbe attracted. One end of one of the coils. is connected to the frontcontact-stop for the armature-lever of relay R. The corresponding end ofthe other coil is connected to the contactstop of a supplementalcircuit-closer, F, operated by the transmitter-lever T.

L B indicate the local battery, connected on one side to thearmature-lever of the relay and to the circuitcloser F and on the otherto the two coils of the differentially-wound sounder.

In the normal condition of the apparatus the parts are in the positionshown. Both coils of the differential sounder are broken,one at the eames front contact of relay R, whose armature-lever is held against itsback stop by its retractor, and the other at the contact-points of thesupplemental circuit-closer F, which is held out of connection with itscontact-stopby the transmitter-lever T, the latter, in the positionshown, being against its back contact-stop and unattraeted by itsoperating electro-magnet. The contact-spring at D being against the hookof the lever and out of contact with the stop connected to battery M B,the line-circuit is to earth through the resistance r, as shown.

The apparatus at station B is the same as at A, and the main battery atthat station has the same pole to line, so thatif both of thetransmitters are operated so as to simultaneously connect the batteriesto line they will neutralize one another. When the key at station A isdepressed so as to operate transmitter T and put the main battery toline the transmitter simultaneously operates the circuit-closer F,allowing its lever to make contact with its stop and close the localcircuit through one of the differential coils simultaneously with theclosing of the circuit for the other coil by the armature-lever of therelay at A, which is of course affected by the outgoing current anddraws forward its lever. The circuit through both coils beingsimultaneouslyclosed,the sounderatAis not affected. At Bthe currentflowsthrough the relay R and closes the circuit through one only of thedifferential coils, which (the other coil being broken at circuit-closerF) causes a signal upon the sounder. In asimilar way, if transmitterT atA be at rest, a current from main battery at B, circulating through therelay of A, the transmitter-lever, and rcsistancer to earth, willoperate the sounder S at A. If battery at B is put to line for thepurpose of giving a signal atA during the time that the transmitter T atthe latter station is in position for sending a signal, both batteries,being to line, will neutralize one another, and the armaturelever of Rat station A will fall back, thus breaking one of the local circuitscompleted when the battery at A was put to line, leaving the other,which is completed through the circuit-closer F, intact. The currentflowing through the differential coil connected to F, being thenunopposed in its action, will draw down the sounder-lever and give thesignal. At station B the signal from A will not be mutilated, because,although the armature-lever may fall against its back contact, breakingthe local coil by which the lever of the sounder is held down, thecircuit through the other coil will be simultaneouslycompleted by theaction of the supplemental circuit-closerF at station B. In order toinsure a uniform action of the transmitter in making and breaking thelocal difl'erential circuit, I sometimes employ the device shown inFig.2. In this device the local differential circuit is broken throughthe intervention of a circuit-closer controlled by an electromagnet, H,the circuit of which in turn is made and broken by the supplementalci'rcuit-closer F, operated by the transmitter. The operation of theapparatus fitted with this appliance does not differ in its generalcharacteristics from that just described, as can be readily seen.

Fig. 3 illustrates the adaptation ofmy invention to a duplex telegraphin which the battery at one station is placed to line with a polaritythe opposite of that with which the battery at the other is connected,so that when the two batteries are simultaneously connected the two willre-enforce one another. Under this arrangement of the batteries, Iemploy a supplemental lever for the relay-armatures. P represents thesupplemental contact-lever, to which the end of the differential coil istaken in the same manner as the end in Fig. 1, which is carried to thefront contact-stop of the armature-lever. Supplemental lever P isnormally held against a contact-stop electrically connected to thecircuit-closer, controlled by the transmitter by means of a springapplied so as to oppose the movement of the'relay-armature lever whenthe latter is attracted by the relay and drawn against the supplementallever. This spring is adjusted to such a tension that,

the supplemental lever cannot be drawn out of contact with its stop bythe action of one main battery only, but can be disconnected by theaction of both batteries combined. The retractor of the relay-armatureallows the lever to be drawn forward by a current from either or both ofthe two distant batteries. One pole of the local battery is connected tothe relayarmature lever and the other to the two coils of thedifferential sounder. Then the relayarmature is against its back stop itis out of contact with the supplemental lever; but when drawn forwardagainst said lever it closes the circuit of one difi erential coil andcompletes one of two breaks in the circuit for the other coil, the otherbreak being at the circuit-closer and breaker controlled by thetransmitter. In the normal position of the parts the circuit of bothcoils is broken, the local-battery circuitv being interrupted at thecontact-point of the relay-armature lever. When the transmitter at, forinstance, station A is operated the relay-armature lever is drawn intocontact with the supplemental lever by the action of the main battery atA, and the circuit-closer F, controlled by the transmitter,simultaneously completes the connection between the end of the lowerdifferential coil on the sounder and the contact-stop for thesupplemental lever..

The one battery being insufficient to disconnect the supplemental leverfrom its stop. the circuit of both differential coils is completed, andthe sounder-lever is unaffected. The circuit from the lower coil isthrough the circuitcloser F, contact-stop of supplemental lever P,supplemental lever, and relay-armature lever, to the local battery. Thecircuit for the upper coil is to supplemental lever P, relay-armaturelever, and to the same pole of the local battery. At the distant stationthe armature-lever makes contact with the supplemental lever,

completing the circuit of one coil only of the sounderviz., theupper-the circuit of the lower coil being interrupted at thecontactpoints of the circuit-closer controlled by the transmitter atthat station, which is in a position of rest. The sounder at thatstation is thus caused to give a signal. It, while the transmitter atthe home station is closed, thus completing the circuit of bothdifferential coils and also putting main battery toline, the transmitter at the distant station be operated, the sounder at the homestation will respond, because, both batteries beingto line, the armaturelever will disconnect the supplemental lever from its stop, thusbreaking the circuit of the local coil connected to the circuit-closercontrolled by the transmitter at the contact-stop of the supplementallever, leaving, however, the circuit of the other coil throughsupplemental lever and armature-leverintact, which latter will act andcause a signal to be given. The sounder-leverat the distantstation,which, by the operation of the transmitter at the home station, has beendrawn against its front stop, will not be affected, because the circuitof the coil connected directly to the supplemental lever will still beclosed, and the transmitter at that station will fail to complete thecircuit of the other, because by the movement of the supplemental leverunder the influence of both batteries the circuit of the coil connectedto the transmitter circuit-closer has been broken at the contact-stop ofthe supplemental lever.

The contacts of the circuit-closing devices in the various parts of allthe diagrams are supposed to be adjustable in the ordinary way, in orderthat the times of making and breaking the local circuits may be adjustedso that the outgoing current shall have no effect upon the sounder.

Other constructions of circuit closing and breaking devices for closingor breaking one of-. the differential coils by the movements of thetransmitter-lever simultaneously with the closing or breaking of theother coil by the action of the relay when affected by the outgoingsignal may be obviously employed without departing from the spirit of myinvention.

It is also apparent that my invention is not limited to a system inwhich two messages only controlled by the relay, and circuit-connections from the other coil through a circuit closer or breakercontrolled by the transmitter, as and for the purpose described.

2. The combination ofa rclay, a transmitter, a differentially-woundreceiving-instrument in alocal circuit, a circuit closer and breakercontrolled by the transmitter and electrically connected with onedifferential coil upon the receiving-instrumen t, and a contact-p ointon the relay electrically connected with the other differential coil. f

3. The combination of a receiving-relay, a local battery, one pole ofwhich is connected to the armature-lever therefor, a differentiallywoundreceiving-instrument whose coils are connected at one end to the otherpole of the battery, relay contact-points controlling one of thedifferential coils, a transmitter, and a circuit closer and breakeroperated thereby in the circuit of the other differential coil.

4. The combination, substantially as dc scribed, upon the sametelegraph-line, of two transmitters, two main-line batteries, one foreach transmitter, two relays in the main-line circuit, and, inconnection with each relay and transmitter atthe same station, adifferen tiallywound receiving-instrument, the circuit of one of Whosecoils is controlled by the relay, while the circuit of the otheris madeand broken by the movements of the transmitter.

Signed at Buffalo, in the county of Erie and State of New York, this25th'day of May, A.

BENJAMIN THOMPSON.

Witnesses:

GEo. O. M. BUcKNER, GHAs. P. FORBUSH.

